Ex-IMF chief Dominique Strauss-Kahn is being probed in a preliminary investigation into an incident that French prosecutors say “could be described as gang rape” that allegedly took place in Washington, D.C., in the winter of 2010, the Agence France-Presse reports.

Prosecutors in Lille, where Strauss-Kahn and three other men have been charged in a pimping case, said that testimony from two Belgian prostitutes could implicate the former head of the International Monetary Fund and the others in gang rape. The preliminary probe was opened on Monday, AFP reported.

One of the two Belgian prostitutes previously said Strauss-Kahn and other men had forced her into a sex act while in Washington in 2010, according to reports from earlier this month. The attack allegedly took place at the W Hotel.

Strauss-Kahn has denied any wrongdoing, saying in a statement this month that he “absolutely contests having committed the slightest act of violence of any nature whatsoever,” according to AFP.

A series of troubling accusations was made against Strauss-Kahn following his arrest last year for allegedly sexually assaulting a hotel maid in New York — charges that have since been dropped. The incident forced Strauss-Kahn to resign as head of the IMFand ended his prospects in the French presidential election.